Synopsis: A strong El Niño is expected to gradually weaken through spring 2016, and to transition to ENSO-neutral during late spring or early summer.
A strong El Niño continued during December, with well above-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean. All weekly Niño indices decreased slightly from the previous month. The subsurface temperatures in the central and eastern Pacific, while still well above average, weakened due to an upwelling equatorial oceanic Kelvin wave. Significant low-level westerly wind anomalies and upper-level easterly wind anomalies continued over much of the tropical Pacific. During the last week, another westerly wind burst occurred in the east-central Pacific. The traditional and equatorial Southern Oscillation Index (SOI) values remained strongly negative. Also, convection remained strong over the central and east-central tropical Pacific, and suppressed over Indonesia. Collectively, these atmospheric and oceanic anomalies reflect the continuation of a strong El Niño episode.
Most models indicate that a strong El Niño will weaken with a transition to ENSO-neutral during the late spring or early summer. The forecasters are in agreement with the model consensus, though the exact timing of the transition is difficult to predict. A strong El Niño is expected to gradually weaken through spring 2016, and to transition to ENSO-neutral during late spring or early summer.
Most landmasses will experience average wind conditions for the month. Winds will be less than average in much of the central and western Pacific Ocean and North Indian Ocean into SE Asia and across much of Africa and southern South America. Around New Zealand will be stronger than normal in the far north as will the western South Pacific through to the far Southwest Pacific through the southern Philippines and Atlantic Oceans and Eastern Europe including the UK.
Much of the northern hemisphere including Europe and the USA, Canada and Europe should be near normal. Most of Australia and southern South America and New Zealand should be slightly to moderately below normal. The Philippines and Gulf States should be above normal.
Cooler outbreaks are forecast for eastern north Asia and warm outbreaks in the Philippines and eastern China and the eastern Caribbean and northern Brazil.
In the western hemisphere extreme precipitation events are forecast for Mexico, and the Southwest and across to Texas and parts of Southern California and parts of the eastern Caribbean and Chile and Bolivia in South America. The Amazon could have unusually low rainfall.
In SE Asia and the South Pacific unusually low rainfall is forecast through the island portion of the region. In Northeast Asia unusually to very unusually high rainfall events are possible in much of China and also in Central Africa and isolated parts of west Asia. Dryness marks much of the Philippines and northeastern Indonesia.
Through much of Europe and Asia usual high to normal conditions prevail except in the UK where the risk of higher rainfall persists.
Unusual low is forecast for parts of Southern Africa. Only far north Queensland and the far north of New Zealand have the risk of unusually high rainfall.
The evolution of ENSO can be viewed through sea surface temperature anomaly maps. The Eastern Pacific is warmer than normal as is the Indian Ocean. The western and central Atlantic is also warmer than normal. The ocean surrounding New Zealand is warmer than normal to the east and north and warmer than normal around most of Australia. The South Pacific remains cooler than normal and is related to ongoing rainfall deficits for the region. The sea in Northeast Asia is also considerably cooler than normal as well as in the northeast Canada while the artic sea is warmer than normal.
Slightly wetter conditions prevail in much of the northern hemisphere with greater anomalies in the Pacific Northwest of the USA and the Caribbean and SE China while drier than normal conditions prevail through the Southwest Pacific region. In the Southern hemisphere dryness is shown for Southern Africa and the Amazon basin and far southern Chile and the South Pacific islands. Wetter than normal conditions prevail in the northern quadrant of the South Pacific along the equator and through the northeast India ocean and into the Indonesian archipelago and the Northern Territory of Australia. Much of North America, Europe and Eurasia is near normal to slightly wetter than normal.
Much of Canada down to the Gulf of Mexico are above normal for temperature while the western States of the USA and Maritime Provinces of Canada are cooler to considerably cooler than normal. Central America and the Caribbean and the northern half of South America are above normal as is the Eastern half of Asia and most of Australia and Southeast Asia and India and southern part of the Middle East. Northeast and southern China and Northern SE Asia is much colder than normal along with much of east Africa and the northern part of the Middle East. Eastern Indonesia through Papua New Guinea and the South Pacific should be slightly cooler than normal. While most of the western half of Australia and New Zealand should be slightly to moderately above normal along with New Zealand. Argentina and southern Brazil should be cooler than snormal.